The Journal of Wildlife Management 1–10; 2019; DOI: 10.1002/jwmg.21774 Research Article Gopher Tortoise Demographic Responses to a Novel Disturbance Regime HUNTER J. HOWELL ,1,2 Department of Biology, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146, USA BETSIE B. ROTHERMEL,2 Archbold Biological Station, 123 Main Drive, Venus, FL 33960, USA K. NICOLE WHITE, Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green Street, Athens, GA 30602, USA CHRISTOPHER A. SEARCY, Department of Biology, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146, USA ABSTRACT The long‐term viability of gopher tortoise (Gopherus polyphemus) populations is jeopardized by increased urbanization and habitat degradation owing to fire suppression. Because the species’ remaining natural habitats in the southeastern United States exist within a mosaic of anthropogenic land uses, it is important to understand demographic responses to contrasting land uses and habitat management regimes. We examined differences in demographic parameters among fire‐suppressed sandhill, restored sandhill, and former sandhill (i.e., ruderal) land use‐land cover (LULC) types at Archbold Biological Station in south‐ central Florida, USA. Using Program MARK, we estimated population size, and sex‐specific and LULC‐specific survivorship based on 6 years of mark‐recapture data. We also analyzed individual growth trajectories and clutch sizes to determine whether growth rates or reproductive output differed among LULC types. Tortoises in an open, ruderal field occurred at a higher density (7.79/ha) than in adjacent restored (1.43/ha) or fire‐suppressed (0.40/ha) sandhill. Despite this higher density, both adult survivorship and body size were significantly higher in the ruderal field. Furthermore, the larger female body size in the ruderal field likely contributed to increased annual survivorship and slightly larger average clutch sizes. We did not detect offsetting negative demographic effects; in particular, we did not find significant biological or statistical differences in body condition, asymptotic body size, or growth rate among the 3 LULC types. Our results suggest that anthropogenic, grass‐dominated land‐cover types may be important components of the habitat mosaic currently available to this at‐risk species. © 2019 The Wildlife Society. KEY WORDS demography, Gopherus polyphemus, habitat management, mowing, population ecology, prescribed fire. The leading causes of biodiversity loss across the globe are generally associated with longleaf pine (Pinus palustris) habitat destruction and degradation, exacerbated by an ex- savanna or sandhill ecosystems (Auffenberg and Franz ponential increase in the human population (Foley et al. 1982, Diemer 1986). The gopher tortoise is a keystone 2011, Haddad et al. 2015). Whereas outright habitat loss has species that alters ecosystems by digging extensive burrow obvious negative conservation implications, effects of habitat systems that serve as habitat for >350 vertebrate and in- fragmentation, and how best to manage small populations vertebrate species (Eisenberg 1983, Jackson and Milstrey isolated by fragmentation, are difficult to assess and are 1989, Witz et al. 1991, Johnson et al. 2017). Despite their debated in the literature (Resasco et al. 2017). Preventing integral role in native ecosystems of the Southeast, gopher isolated populations from dropping below a minimum viable tortoises, like most other turtles, are threatened by decades population size is important to avoid extinction vortexes and of habitat loss, poor habitat management, and human har- to ensure long‐term species persistence to maintain global vest, which have caused declines across their range (Diemer biodiversity (Shaffer 1981). In many instances, however, it 1986, Klemens 2000, Ernst and Lovich 2009, Lovich et al. may not be possible to implement the management strategy 2018). The greatest current threats to the species’ viability that would be most beneficial to the species in question are habitat loss, caused by increased urbanization, and because of resource limitations, stakeholder conflicts, the habitat degradation due to fire suppression (Mushinsky socio‐political climate, or a combination of these factors et al. 2006). Overgrown forest conditions, resulting from (Wilson et al. 2006, Traill et al. 2010). lack of appropriate fire management, have led to lower Gopher tortoises (Gopherus polyphemus) are denizens of the tortoise densities, more abandoned burrows, and decreased southeastern Coastal Plain of the United States and are population sizes (Auffenberg and Franz 1982, Diemer 1989). Range‐wide habitat fragmentation and associated habitat degradation have led to many populations inhabiting Received: 19 March 2019; Accepted: 10 September 2019 habitat islands surrounded by agricultural or urban land uses 1 ( ) E‐mail: [email protected] Mushinsky and McCoy 1994, Ennen et al. 2011 . Within 2These authors contributed equally to the manuscript. these islands, a lack of surrounding habitat is coupled with Howell et al. • Gopher Tortoise Demography in Modified Sandhill 1 behavioral avoidance of adjacent closed‐canopy vegetation, of the Lake Wales Ridge in Highlands County, Florida which leads to skewed densities and increased population (27.19°N, 81.34°W). The study area has a subtropical cli- isolation (Mushinsky and McCoy 1994, McCoy and mate with >60% of annual precipitation falling during the 4 Mushinsky 2007, McCoy et al. 2013). Because of these wettest months (Jun–Sep). Between 1958 and 2017, annual threats, the gopher tortoise is federally listed as threatened rainfall averaged 1,355 mm, with mean monthly rainfall of in the extreme western portion of its range and currently 168 mm during May–October and 57 mm during under review for listing in the remaining eastern portion of November–April. Mean daily maximum and minimum its range (U.S. Fish and Wildlife Service 1987, 2011). temperatures were 32.8°C and 19.3°C in summer and Ideally, gopher tortoise habitat is managed predominantly 26.1°C and 11.0°C in winter (ABS manual weather data, through the application of prescribed fire to reduce mid‐story 1958–2017; www.archbold‐station.org/data/, accessed 8 vegetation, increase spacing between canopy trees, promote Jul 2019). production of herbaceous groundcover, and increase thermo- A slash pine‐turkey oak (Pinus elliottii var. densa–Quercus regulatory opportunities (Diemer 1986, Yager et al. 2007). laevis) vegetation community, known as southern ridge Habitats with dense herbaceous groundcover comprised of sandhill, occurs on the well‐drained, sandy soils of Red Hill abundant grasses, legumes, and other nutritious, low‐growing at elevations of 54–64 m (Abrahamson et al. 1984; Fig. 1). plants provide optimal food resources for gopher tortoises Historically, the modal fire return interval for this py- (MacDonald and Mushinsky 1988). The use of prescribed fire, roclimax community was 2–5 years, whereas the sur- however, is plagued with concerns about smoke management, rounding sand pine (Pinus clausa) scrub would have burned lowered air quality, potential damage to private property, and infrequently, on the order of every 20–100 years (Menges poor public perception, particularly in urbanized areas (Yager et al. 2017). Following a severe wildfire in 1927, however, et al. 2007, Yoder et al. 2007).Asaresult,fire suppression has fires on Red Hill were actively suppressed until ABS ini- become a widespread management problem for many py- tiated a prescribed burning program and began re- roclimax species, including the gopher tortoise. introducing fire to selected sandhill units between 1989 and In Florida, USA, a stronghold of the gopher tortoise’s 1993 (Ashton et al. 2008). remaining populations (Allison and McCoy 2014), losses of The management units within our 136‐ha study area can native uplands exceed 80% (Sprott and Mazzotti, 2001), be categorized into 3 land use‐land cover (LULC) types: and the remaining natural land cover falls within a mosaic of fire‐suppressed sandhill, restored sandhill, and ruderal agricultural and urbanized land uses (Diemer 1987). Within (Fig. 1). Nearly half of the fire‐suppressed sandhill area has the Lake Wales Ridge, a fire‐adapted scrub and sandhill not burned since 1927, and the remainder has been burned ecosystem vital for gopher tortoises in central Florida, ap- only 1–3 times since 1989. As a result of decades of fire proximately 85% of native vegetation has been lost through suppression, cover of sand pines increased, creating closed‐ urbanization and agricultural development (Turner et al. canopy conditions and reducing herbaceous groundcover 2006). As Florida’s human population continues its rapid (Ashton et al. 2008). Areas categorized as restored sandhill growth (U.S. Census Bureau 2017), the amount of gopher were historically fire‐suppressed but have been undergoing tortoise habitat that becomes part of the non‐native matrix restoration since 2013 using a combination of mechanical will continue to increase. Understanding how to manage clearing and prescribed fire (2–3 burns between 2012 and remnant habitats in an urbanized or agricultural matrix, 2017). Hill Garden, a 4.5‐ha unit of ruderal vegetation on where there may be resistance to use of prescribed fire, will the top of Red Hill, has been maintained for several decades be critical to ensuring that these areas can support viable as an open field by mowing. Initially cleared in the 1940s, tortoise populations into the future. the unit was planted